In a system which transmits voice in real time, there is technology which replaces voice data with data other than voice, and mutes (or repeats) the voice when the data other than voice is transmitted. For example, in STF-27 of ARIB currently explained in standard of digital automobile telephone systems issued by Association of Wireless Industries and Businesses (ARIB STANDARD) part I (RCRSTD-27 J version) (for example, FIGS. 4.15.2 to 4), which is a prior art document, such control that replaces voice data with FACCH (Fast Associated Control Channel) by providing a steal flag in a part of data which is framed, and setting the steal flag when there is data to be sent at high speed is performed.
In SCPC (Single Channel per Carrier) communication where half-duplex communication is a base such as a wireless, when it is desired to perform communication based on framed digital transmission, a function called “follow-up participation” may pose a problem. The follow-up participation means entering in a call in the middle of a call when one-many communication (group call) is performed in particular, and can hear the call performed to the many from the middle, for example, when a certain terminal moves to a strong electric field area from a weak electric field area. A group call is a function that data (address) of a group number and the like is sent at the time of a call start and only what have the address coinciding with the data can speak over the telephone, and even if carrier frequencies of respective terminals coincide, content of the call received is not reproduced when the group number and the like do not coincide.
Analog radios which were mainstream up to the conventional performed this processing using various methods. For example, a group was discriminated by separating 300 Hz or less of voice as a subvoice band from a usual voice band, and feeding a tone signal to this band, and the like. For this reason, it was easily attained that a certain terminal could perform the follow-up participation in a call.
On the other hand, a transmitter using digital SCPC (Single Channel Per Carrier) performs communication by transmitting a group number at high speed at the time of a call start, and then, arranging the group number in distinction from voice data in one frame, or dividing the group number to transmit it in several frames, and receiving the group number divided and transmitted over several frames, and linking them together and the like at a receiving end. For this reason, a follow-up participant can do the follow-up participation only in the timing of one frame or more.
There is a tendency that capacity (bit rate) of being transmittable digitally is in a cutback direction for one frame to become long due to efficiency increase of frequency utilization in these days. This is because a transmission efficiency deteriorates since a ratio of data (synchronous word etc.) which should be transmitted by one frame becomes large when one frame is made small.
In a system in which one frame is long and a low bit rate is damaged in this way, timing when the follow-up participation can be performed decreases, and hence, the follow-up participation becomes slow as a result.
A similar problem arises similarly not only when repeatedly transmitting a group number for follow-up participation, but also when repeatedly transmitting various control data stealing voice data, and hence, a method of transmitting efficiently both of the voice data and the control data which should be repeatedly transmitted is desired.
This invention is made in view of the above-mentioned actual circumstances, and sets it as a first object to enable efficient transmission of voice information and control information.
In addition, this invention sets it as a second object to make the follow-up participation easy.
Furthermore, this invention sets it as a third object to make it possible to transmit control information without dropping transmission efficiency of voice information.
In order to achieve the above-described invention object, a communication method which relates to a first aspect of the present invention includes a step of sequentially inputting voice data to be a transmission object, and discriminating whether the voice which is indicated by the inputted voice data is silent, a step of replacing the voice data which is discriminated that it indicates silent voice with predetermined data, and a step of performing wireless transmission of the predetermined data being replaced, with voice data indicating voice, at a transmitting end, and, a step of receiving the signal to be wireless transmitted, a step of discriminating the voice data and the predetermined data of the received signal, and a step of reproducing the voice data in the voice data, reproducing a silence in the predetermined data, and further executing processing based on the predetermined data, at a receiving end.
In the communication method of the present invention, preferably, the above-mentioned transmitting end further includes a step of forming a transmission frame from the above-mentioned voice data and the above-mentioned predetermined data being replaced, and a step of setting a steal flag which shows the presence of the predetermined data at the time of transmission, and the receiving end further includes a step of discriminating the presence of predetermined data on the basis of the steal flag in the received signal.
A communication method which relates to a second aspect of the present invention includes a step of sequentially inputting voice data to be a transmission object, a step of discriminating whether the voice which is indicated by the inputted voice data is silent, a step of replacing the voice data which is discriminated that it indicates silent voice with predetermined data, and a step of transmitting voice data indicating sonant voice, and the predetermined data being replaced, together.
A communication method which relates to a third aspect of the present invention includes a step of receiving a signal to be wireless transmitted, a step of discriminating voice data and the predetermined data which replaces voice data and is transmitted, in the received signal, a step of reproducing the voice data in the received voice data, and reproducing silence in the predetermined data replaced and transmitted, and a step of executing control processing based on the predetermined data replaced and transmitted.
A transmitting apparatus which relates to a fourth aspect of the present invention includes input means of inputting voice data, means of discriminating whether voice data inputted by the above-mentioned input means satisfies a predetermined non-transmission condition, replacement means of replacing voice data discriminated by the discrimination means that the voice data does not satisfy the non-transmission condition, with predetermined data by stealing, and transmission means of transmitting the voice data and the predetermined data being replaced.
In the transmitting apparatus of the present invention, it is preferable that the above-mentioned non-transmission condition is that voice data is silent voice data and a level of voice which the voice data indicates is a reference level or less, and that the above-mentioned replacement means operates so as to replace the silent voice data, or the voice data which is in the reference level or less, with the above-mentioned predetermined data.
Furthermore, more preferably, in the transmitting apparatus of the present invention, the above-mentioned replacement means includes means of composing a transmission frame including voice data discriminated by the above-mentioned discrimination means that the voice data does not satisfy the above-mentioned non-transmission condition, the above-mentioned predetermined data, and a control flag which shows the presence of the predetermined data, and the above-mentioned transmission means operates so that a signal may be transmitted by the above-mentioned frame unit.
A receiving apparatus which relates to a fifth aspect of the present invention includes receiving means of receiving a signal including an voice signal, detection means of detecting predetermined data replaced from an voice signal arranged in the signal received by the receiving means, reproduction means of reproducing the voice signal received by the receiving means, and further reproducing predetermined voice when predetermined data is detected by the detection means, and control means of executing processing based on the predetermined data detected by the above-mentioned detection means.
In the receiving apparatus of the present invention, it is preferable that the above-mentioned receiving means operates so as to receive a frame signal, that the above-mentioned detection means operates so as to detect predetermined data in an voice signal included in the above-mentioned frame signal, that the above-mentioned reproduction means operates, so as to reproduce the voice signal in the above-mentioned frame signal which is received by the above-mentioned receiving means, and further to reproduce the predetermined voice detected by the above-mentioned detection means, by the above-mentioned detection means, and that the above-mentioned control means of executing processing based on the predetermined data detected by the above-mentioned detection means.
In the receiving apparatus of the present invention, it is more preferable that a predetermined control flag which shows the presence of the above-mentioned predetermined data is set in the above-mentioned frame signal, and that the above-mentioned detection means operates so as to detect the above-mentioned predetermined data on the basis of the above-mentioned predetermined control flag.
Since the present invention adopts the above-mentioned configurations, it becomes possible to repeatedly transmit predetermined data (voice and control information data) efficiently without degrading communication quality so much.